Liquid dispenser foam limiting element

ABSTRACT

A foam limiting element for a dispenser for liquids is provided. The element comprises a three-dimensional mesh of a multiplicity of the fibers which are connected together to create a multiplicity of irregular liquid paths through the spaces between the fibers, the element having a three-dimensional configuration to fit within a dispensing head of a dispenser. A dispenser for liquids has a dispenser head with a discharge channel in which a foam limiting element is positioned. The discharge channel has means for retaining the element in place whereby all liquid flows through the element before being dispensed. The discharge channel has a wall structure which precludes introduction of air into the liquid to be dispensed.

FIELD OF THE INVENTION

The present invention relates to a foam control element for use in thedispensing head of a dispenser for liquids which tend to foam upon beingfilled into individual containers. The invention also relates to adispenser with a foam control element.

BACKGROUND OF THE INVENTION

It is well known to dispense liquids, neat or diluted with water, from abulk container into smaller, individual containers, for example inindustrial kitchens, hotels and the like where various cleaning productsare dispensed into small containers for use by individual members of thecleaning staff. An example of a dispenser for use in this fashion isdescribed in European Published Patent Application 564,303 in the nameof Diversey Corporation. The liquid being dispensed tends to foam due toagitation and turbulence, which often tends to be the case with cleaningliquids which are inherently susceptible to foaming. A problem arises inthat the individual containers become partly filled with foam as theliquid is poured or dispensed into the container. Either the containershave to be only partly filled with liquid or the foam is forced tooverflow while more liquid is dispensed into the container. Obviously,neither of these alternatives is at all satisfactory.

The creation of foam can to some extent be reduced by directing the flowof liquid to the side of the container, rather than in the middle whereit tends to agitate the liquid already in the container. Examples ofsuch dispensing heads are described in U.S. Pat. Nos. 3,757,835,4,512,379 and 4,574,853. But, even this measure limits the formation offoam to only a small extent. Moreover, in many types of dispensers, itis simply not possible to direct the flow of liquid in this way.

It is also known to fit flow reducers in nozzles which dispense foamingproducts. Such flow reducers incorporate one or more apertured screensacross the direction of flow. Examples of these types of dispensers aredescribed in U.S. Pat. Nos. 3,698,452; 3,805,856 and 4,553,574. It hasbeen found that these screens reduce foaming to only a limited extentand then only at relatively low delivery pressures.

There are various types of nozzle attachments for water spouts whichhave wire screen mesh, open cell foam, perforated plate and the like,where such attachments are designed to aerate the flow of water tominimize thereby splashing of water as it flows under pressure. Examplesof such aeration devices are described in U.S. Pat. Nos. 2,515,600;2,929,567; 2,995,309; 2,998,930; 3,239,152; 3,428,258; 3,642,213;3,707,236; 3,730,439; 4,119,276 and 4,730,786. Although these aeratordevices are useful for reducing water splashing, they are not acceptablefor use as foam control devices because, by introducing air bubbles tothe liquid flow, foaming of susceptible liquids would be increased.

The object of the present invention is to provide a foam control elementwhich is relatively simple and relatively inexpensive and yet stillproduces a significant foam reduction effect.

Accordingly, the invention provides a foam control element comprising athree-dimensional mesh of a multiplicity of fine fibers which areconnected together to create a great plurality of irregular liquid pathsthrough the spaces between the fibers.

The invention also provides a dispenser for foaming liquids which isfitted with such a foam control element.

The inventors have found that a section of a three-dimensional mesh offine fibers is very effective in reducing foaming of liquids beingdispensed into containers. This mesh, which is commonly used forscouring pads for example, is readily available and relativelyinexpensive. It might have been expected that such a mesh would have apoor effect on flowthrough of liquid, or would create blockages, but theinventors found that this was not the case. Sections of the mesh can beeasily fitted in the outlet nozzles of existing dispensers and cansignificantly reduce foaming, thereby increasing the efficiency of thedispensers and avoiding hazardous and troublesome spillages.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a foam control elementfor a dispenser for liquids is provided. The element comprises athree-dimensional mesh of a multiplicity of fine fibers which areconnected together to create a multiplicity of irregular liquid pathsthrough the spaces between the fibers, the element having athree-dimensional configuration to fit within a dispensing head of adispenser.

In accordance with a further aspect of the invention, a dispenser forliquids has a dispenser head with a discharge channel in which a foamcontrol element is positioned. The discharge channel has means forretaining the element in place whereby all liquid flows through theelement before being dispensed. The discharge channel has a wallstructure which precludes introduction of air into the liquid to bedispensed.

In accordance with another aspect of the invention, a method ofdispensing liquids from a dispenser having a foam control elementcomprising a three-dimensional mesh of a multiplicity of fine fiberswhich are connected together to create a great plurality of irregularliquid paths through the spaces between the fibers, the minimumthickness t_(min) (mm) of the element being determined by the equation:

    t.sub.min =(p×f)/.sub.xd

where p = pressure (psi) under which liquid is dispensed

f = fibre fineness (decitex)

d = density (kg/m³)

x = 5, 10 or 20

The invention will be better understood from the following detaileddescription and the examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are described with respect to thedrawings wherein:

FIG. 1 is a schematic of a dispenser used for filling containers;

FIG. 2 is a enlarged section through the dispensing head of thedispenser of FIG. 1;

FIG. 3 is a graph showing the effect of fibre thickness on controllingfoam levels;

FIG. 4 is a graph showing the effect of pad thickness of the foamlevels; and

FIG. 5 is a graph showing the effect of pad density on foam levels.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The dispenser, such as described in the aforementioned Europeanpublished application 564,303, comprises a dispensing head 1 controlledby a magnetically operating valve 2. Concentrate C and water W are fedto a venturi 3. In the water line there is a back flow preventer (checkvalve) 4.

The form of the dispenser is not central to the invention and so it willnot be described in detail; the person skilled in this art will wellunderstand the operation of this and other types of dispensers.

In FIG. 2 the dispensing head i is enlarged in section. The foam controlelement 5 is fitted at or near the outlet for the dispensing head, abovebottle 6. The element diameter, according to this particular embodiment,is approximately 12 mm where it is appreciated that its dimensions mayvary depending upon its application.

The valve 2 is open and closed depending upon the position of the bottle6 which is supported by a cradle, not shown. When the bottle is empty,the cradle lifts the bottle upwardly to move the dispensing head in adirection which opens the valve 2. Water then flows in through line 8upwardly through line 10 and through the check valve 4 back down intothe venturi 3. The purposes of the venturi 3 is to draw concentratethrough line 12 and mix it with the water to provide a mixed solution inline 14 which passes through the dispensing head 1. As shown in moredetail in FIG. 2, the dispensing head 1 has the foam control elementpositioned within the discharge region generally designated 16 which isin direct fluid communication with the inlet pipe 14. As will becomeapparent from the following examples, the foam control element 5 ispositioned in the discharge region 16 of the dispensing head to minimizethe turbulence in the flow of liquid as it discharges from thedispensing head into the container 6. As will be appreciated from therelationship shown in FIG. 2, the container neck portion 18 surroundsthe outlet disc 20 of the discharge region 16 when the container ispushed upwardly to contact the switch mechanism 22 which opens the flowcontrol valve 2. The conduit 14, as it leads directly from the venturi 3into the dispensing head 1, does not have any provision for air inlet,nor does the L-shaped channel 24 have any provision for air inlet. Henceno air is drawn into the flow of liquid above or immediately beneath thefoam control element 5. Hence the dispensing head 1 is designed with theL-shaped channel 24 to ensure that no air enters the flow of liquidbefore flowing into the container 6. In this manner, foaming is furtheravoided by the failure to introduce air into the system in the region ofthe foam control element 5.

As will become apparent from the investigations undertaken andsummarized in the following examples, there are various characteristicsof the foam control element which provide this significant reduction infoam height when containers are filled with liquids which are normallysusceptible to foaming during the filling operation. Although the foamcontrol element is described in terms of the fibre structure commonlyfound in scouring pads, it is appreciated that the foam control elementmay comprise any arrangement of three-dimensional mesh of fine fiberswhich provide irregular-shaped channels through which the liquid mustflow, as is provided in the standard type of scouring pad. The finefibers for the three-dimensional mesh may be of plastics material, andas later defined, preferably of Nylon®. The fibers may also be ofultrafine spun glass or drawn metal wire. The fine fibers of the meshare randomly oriented throughout the thickness of the mesh and acrossthe surface of the mesh, such random orientation lending to theprovision of the irregular-shaped channels through which the liquid mustflow in being dispensed through the dispensing head. Hence the randomorientation of the fibers is preferred, since it would be prohibitivelyexpensive to provide the irregular-shaped channels with an orderedarrangement of the fine fibers. Furthermore, the random orientation ofthe fine fibers is further provided in that there is no predefinedlongitudinal shape for the fibers; that is, they can be looped,intertwined, and crossing over one another where there are few straightportions in the longitudinal direction of the fibers. Hence, the generaldescription of the element as being a three-dimensional mesh of the finefibers where the fibers are provided in the mesh in a randomorientation.

The foam height controlling properties of the foam control element arebelieved to be due to this three-dimensional format of the fine fibers.Hence the fibers need not be of plastic, although plastic is preferred,and instead the fibers may be of glass or metal which arecorrespondingly randomly oriented to provide the same spatialcharacteristics of the three-dimensional mesh commonly found in scouringpads.

As will be defined in the Examples, the fineness of the fibre can bemeasured in Decitex units which is the weight of the three-dimensionalmesh in grams when the mesh is made from 10,000 meter of the fibre. Thepad thickness shall be defined in millimeters and the pad density shallbe defined in kilograms per meter³. Two of the characteristics of thethree-dimensional pad include the ratio of the fineness of the fibre tothe product of the pad thickness and pad density. A furthercharacteristic is in determining the pad thickness by dividing theproduct of the pressure in pounds per square inch and fineness of thefibre by a constant times the pad density, where the constant preferablyranges in value from about 5 to about 20 depending upon thesusceptibility of the liquid to foaming; i.e., ranging from a highlyfoaming liquid to a slightly foaming liquid.

The structural characteristics of the foam control element 5 aresufficient to ensure integrity of the three-dimensional mesh while inuse. It is understood, however, that in achieving the various desiredcharacteristics of the foam control element, the diameter orcross-sectional dimension of the foam control element may exceed its owninherent support characteristics; hence requiring a support grid or thelike on the discharge side of the foam control element. Such grid,although not shown in FIG. 2, would support the foam control elementwhen its cross-sectional dimension exceeds its own inherent ability toremain reasonably flat as captured within the dispensing head. The gridfor supporting an enlarged foam control element is designed to minimizeinduction of turbulence into the flow after it leaves the foam controlelement.

It is appreciated that, from time to time, replacement of the foamcontrol element may be required. Although not shown in FIG. 2, thedischarge portion 16 of the dispensing head would be removable to allowaccess to the foam control elements so that it may be removed and a newone inserted in its place.

The means for retaining the foam control element in the dischargechannel 24 may be a recessed groove 26 which is formed in the solidsidewalls 28 of the discharge channel. The size of the groove 26 is suchto retain the foam control element in position.

EXAMPLE 1

Comparative tests were conducted on the filling of a hand dish-washingchemical diluted 1 to 10 with water ("Divoplus" available from DiverseyLimited, Watford, UK) into 2 liter bottles from a standardventuri/dispensing head assembly. The water was provided at a pressureof 40 psi.

a) No foam control. Upon filling of the bottle, a very significantamount of foam was created. The height of the foam from the liquid levelto the top of the bottle was 122 mm.

On inspection of the filling process, it was concluded that the highlevel of foam production may be due to the flow breaking up as it leftthe dispensing head. This resulted in the flow entering the liquidalready in the bottle as a plurality of individual turbulent flows or asindividual drops. This caused more air to be drawn into the liquid,resulting in more foam.

It was thought that to prevent this phenomenon occurring, the flowshould be caused to enter the existing liquid in a single column, withminimum kinetic energy turbulence.

Different measures to try and achieve this were tested.

b) Flow divider. A flow divider similar to that used on domestic watertaps was fitted on the outlet from the dispensing head. The dividerconsists of a number of thin vanes parallel to the flow, with a secondset at right angles to form a grid effect. This device did improve theintegrity of the flow, but no appreciable decrease in foam level wasobserved.

c) Plastic mesh. Two types of plastic mesh were fitted, separately, atthe outlet. Both were formed of cross-members of 1 mm diameter, and thehole size was either 1.5 mm square or 3 mm square. No appreciabledecrease in foam level was observed.

d) Pellets. A 15 mm section of tube filled with pellets 3 mm long and 2mm in diameter was fitted immediately upstream of a mesh as described intest c). No significant improvement was observed.

e) Metal filter. A disc of 400 AM stainless steel mesh was fitted at thedispenser outlet. The integrity of the flow was improved but a largeamount of turbulence was still seen in the liquid column leaving theoutlet. There was a slight improvement in foam level: the foam heightwas 105 mm from the liquid level to the top of the bottle.

f) Double metal filter. Two of the discs described in test e) were used,with a spacing of 2.5 mm therebetween. There was a similar improvementin flow, but with significant turbulence being visible. There was afurther slight improvement in foam level: foam height decreased to 84mm.

g) Three-dimensional mesh of fine fibers, for example as used inscouring pads. A disc formed from a domestic scouring pad was fitted atthe dispensing outlet. The liquid flow was observed to be reduced to asingle column only minimal movement and turbulence could be seen in thecolumn. The was a dramatic decrease in foam height: only 20 mm foamheight was measured.

CONCLUSION: the use of a three dimensional mesh of fine fibers, forexample a section of scouring pad material, can very significantlyreduce the foaming of liquids dispensed into containers.

EXAMPLE 2

Comparative tests were done, using the same filling conditions as inExample 1, to determine the effect of changing the position of the fibremesh sections relative to the dispensing outlet.

a) The pad was placed immediately downstream of the venturi, at the exitto the dispensing head. The flow path through the dispensing head wasrelatively tortuous. A large amount of foam was produced.

b) The pad was placed immediately upstream of a section of plastic meshat the dispenser outlet, the mesh being as described in Example 1 c). Alarge amount of foam was produced.

CONCLUSION: anything downstream of the pad which increase turbulencewill reduce the effectiveness of the pad; an important factor is thefinal surface which the liquid encounters before it leaves the dispenserand falls into the container.

EXAMPLE 3

Comparative tests were conducted to determine the effect of fibrethickness in the fibre mesh section. The filling procedure was asbefore, again with "Divoplus" concentrate diluted 1 to 10 with water.The tests were conducted at three different pressures, 20, 50 and 80psi, to see if similar relative effects are achieved at variouspressures. Of course, more foam was expected to be produced at increasedpressures, and indeed this turned out to be the case, but reduction infoam levels even at higher pressures was hoped for with the use of thefibre mesh sections.

The liquid was delivered from the dispensing head into a measuringcylinder. The cylinder was filled with liquid and foam to the litermark, 350 mm from the bottom. The foam was allowed to settle for a fewseconds and then its height above the liquid surface was measured.

Three different sections of fibre mesh were tested, namely scouring padsavailable commercially as Vileda 4600, Vileda 4360 and Vileda 4370.Vileda 4600 is formed of 20 decitex fibers, 4360 is a mixture of 20 and60 decitex fibers, and 4370 of 60 decitex fibers. The pad thicknesseswere the same, approximately 9 mm, and the packing densities wereapproximately the same, about 160 g/m² ; the real density (g/m³) wasthus approximately 18,000 g/m³.

The results of the tests are shown on FIG. 3 and are also given below.

    ______________________________________                                        a)    Vileda 4600: decitex                                                          water Pressure (Psi):                                                                           20      50   80                                             Foam Height (mm): 10      55   90                                       b)    Vileda 4360: 20 and 60 decitex                                                Water Pressure (Psi):                                                                           20      50   80                                             Foam Height (mm): 25      90   115                                      c)    Vileda 4370: 60 decitex                                                       Water Pressure (psi):                                                                           20      50   80                                             Foam Height (mm): 45      100  120                                      ______________________________________                                    

CONCLUSION: at all pressures a pad formed of finer fibers performsbetter than a pad of coarser fibers (pad made of fibers of differentfineness are believed to behave similar to a pad with fibers of theaveraged valve of the different fineness). At higher pressures,significantly more foaming occurs.

EXAMPLE 4

Comparative tests were conducted to determine the effect of thethickness of the sections of fibre mesh. Pads of Vileda 4600 weretested, at three different thicknesses. The filling conditions and otherparameters were as in Example 3.

The results of the tests are shown in FIG. 4 and are also given below.

    ______________________________________                                        a)    18 mm thickness                                                               Water Pressure:                                                                           20          50   80                                               Foam Height:                                                                              10          25   50                                         b)    9 mm thickness                                                                Water Pressure:                                                                           20          50   80                                               Foam Height:                                                                              10          55   75                                         c)    4 mm thickness                                                                Water Pressure:                                                                           20          50   80                                               Foam Height:                                                                              50          115  135                                        ______________________________________                                    

CONCLUSION: the foam level decreases with increasing thickness of pad,although at lower pressures the difference between pads is slight.

EXAMPLE 5

Comparative tests were conducted to determine the effect of fibre meshdensity. Pads of 9 mm Vileda 4600 were compressed to thickness of 5 mmand 2 mm in order to approximately double and quadruple the densities.The filling conditions were as before.

The results of the tests are shown in FIG. 5 and are also given below.

    ______________________________________                                        a)    Single density (9 mm)                                                         Water Pressure: 20        50  80                                              Foam Height:    10        65  110                                       b)    Double density (5 mm)                                                         Water Pressure: 20        50  80                                              Foam Height:    10        70  95                                        c)    Quadruple density (2 mm)                                                      Water Pressure: 20        50  80                                              Foam Height:    10        65  85                                        ______________________________________                                    

CONCLUSION: the increased foaming which would be expected with a smallerthickness (see Example 4) is almost entirely cancelled out by theincreased density. At all except the highest of pressures, the foamlevels at all three tested densities is almost the same. Taking intoaccount the decrease in thickness, it can be concluded that increaseddensity leads to lower foam levels.

OVERALL CONCLUSIONS

a) Three dimensional meshes of fine fibers can be used to significantlyreduce foam levels when filling containers.

b) Such meshes work better when formed of relatively fine fibers closetogether than when formed of coarser fibers further apart (i.e. for thesame density, lower decitex fibers are better).

c) Increasing thickness of the mesh reduces foam levels.

d) Increasing density of the mesh (while keeping the fibre thicknessconstant) reduces foam levels.

e) The pressure driving the liquid through the dispenser outlet is acritical factor. To some extent, foam levels for most liquids can becontrolled by operating at relatively low pressures, though even at lowpressures the use of the tested pads will still reduce the foam level.Moreover, in practice, dispensers are often intended to be used over arange of pressures, depending on where the dispenser is operating, andit is not also feasible or desirable to fit pressure regulators tocontrol the pressure.

On analyzing all of the results of the comparative tests carried out,the inventors have found that the effectiveness of the fibre mesh padscan be suitably defined by considering the ratio of the fineness of thefibre making up the mesh to the product of the mesh pad thickness andthe mesh density.

The analysis of the ratio f/_(txd) relies to some extent on assumingthat the lines plotted on FIGS. 3 to 5 are linear and parallel, but itis believed that this simplification is justified.

The inventors have found that with a liquid of the type tested in theexample, for a pad to work effectively in reducing foam over a range ofhigh and low pressures, for example a range of from 20 to 80 psi, thenthe ratio f/_(txd) should be less than 0.15.

Thus taking the pads tested in Example 3, it can be seen that with t=9mm and d=18 kg/m³, the fineness f should be less than 24 decitex.

For pads to work effectively only at lower pressures, i.e., less than 20psi, the inventors have found that the ratio f/_(txd) need not be lessthan 0.3.

Thus, taking again the pads tested in Example 3, it can be seen thatwith t=9 mm and d=18 kg/m³, the fineness f should be less than 48decitex.

In another analysis of the test results, the inventors found that onfactoring in the operating pressure p (measured in psi), it wasadvantageous if the ratio p×f/_(txd) equalled approximately 10.

This analysis leads to a means of selecting the minimum thickness of apad of known fineness and density f for use at a particular operatingpressure. Thus, the inventors found that the minimum pad thickness couldusefully be selected by considering the equation: ##EQU1##

For example, at a pressure of 20 psi, with f=20 and d=18 kg/m³, t_(min)=2.2 mm; at 80 psi, t_(min) =8.8 mm.

For a pad of fineness f=60, and d=18 kg/m³, t_(min) =6.6 mm at 20 psiand 26 mm at 80 psi.

The relationship for calculating t_(min) is very useful when theparameters of the relationship are known. The maximum thickness for thefoam control element is usually determined by the geometry of thedispensing head, where it is appreciated that few benefits are obtainedby providing a foam control element thickness far in excess of t_(min).Therefore for most dispensing head configurations and the normal rangeof pressure consideration, the maximum thickness of the foam controlelement is from approximately 10 to 50 mm.

In Example 1, it is noted that at 40 psi, the foam control elementprovides a foam height of only 20 mm. This result is comparable to theresult obtained with the 18 mm thick element as shown in FIG. 4. Thefoam height with no control element was 122 mm as reported in Example 1.Hence, the foam control element reduces foam height by as much asfive-sixths of the foam height in a normal uncontrolled dispensingoperation. This foam height standard can be used as an alternative tothe specific ratios discussed above in selecting fine fibre meshes whichare useful in controlling foam. Thus, a method of selecting suitablepads of a fine fibre mesh is to select a pad thickness for a mesh of agiven fineness and density which, for the operating pressure and liquidunder consideration, will give up to one-sixth of the level of foam thatis developed without the pad (and without other foam controlmechanisms). This practical test for choosing pad parameters could beeasily adopted in most dispensing and filling stations.

The comparative examples described in this application were conductedusing a liquid which can be described as being moderately foamy.Obviously, there are other liquids which will be more or less foamy.

The inventors believe that liquids to be filled into containers can bebroadly characterized as being either slightly foamy, moderately foamyor highly foamy. In relation to the ratios discussed above for themoderately foamy liquid, the inventors consider that they can be variedby a factor of two either way for slightly foamy and for highly foamyliquids.

Thus, for slightly foamy liquids, f/_(txd) should be less than 0.3 for alarge range of pressures or less than 0.6 for lower pressures.

For highly foamy liquids, f/_(txd) should be less than 0.075 for a largerange of pressures or less than 0.15 for lower pressures.

When selecting pad thicknesses for a given operating pressure, t_(min)=pxf/₂₀×d for slightly foamy liquids and t_(min) =pxf/₅×d for highlyfoamy liquids.

The three-dimensional meshes of fine fibers which are used in the foamcontrol elements of the invention are preferably formed in aconventional fashion, in the same way that scouring pad material isproduced. The production method is understood to consist of the cardingof fibre strands into mats and the stitching together of several mats tocreate a thick sheet. The sheet is sprayed with a binder to fix thefibers, the spraying operation optionally including abrasive materialsto give the scouring effect of the finished product. The sprayed sheetsare cut up into sections when dry. It is, of course, appreciated thatthe abrasive materials on the fibers are not required to effect foamcontrol in accordance with this invention.

The fibre material is routinely Nylon 66®, but it can be a differentplastics material, finely spun glass fibre or finely drawn wire wheresuitable alternatives will be evident to the person skilled in the art.Similarly, alternative methods of forming three-dimensional meshes offine fibers will be apparent to those skilled in the art and thisinvention is not limited to the meshes which are used in scouring pads.

Although preferred embodiments of the invention are described herein indetail, it will be understood by those skilled in the art thatvariations may be made thereto without departing from the spirit of theinvention or the scope of the appended claims.

We claim:
 1. A foam control element configured for use in a dispenser for liquids which tend to foam when dispensed, the element comprising a three-dimensional mesh of multiplicity of fine fibres which are connected together to create a multiplicity of irregular liquid paths through the spaces between the fibres, the ratio of the fineness f (decitex) of the fibres to the product of the element thickness t (mm) and the element density d (kg/m³) being less than 0.6, said element having a three-dimensional configuration to fit within a dispensing head of a dispenser, whereby said foam control element when in use in absence of air flowing therethrough reduces foam height when a container is filled with such liquid.
 2. A foam control element according to claim 1, wherein f/_(txd) <0.3.
 3. A foam control element according to claim 1, wherein f/_(txd) <0.15.
 4. A foam control element according to claim 1, wherein f/_(txd) <0.075.
 5. A foam control element of claim 1, wherein said three-dimensional configuration is cylindrical.
 6. A method of dispensing liquids from a dispenser through a foam control element for reducing foam height of liquids dispensed into a container, said element comprising a three-dimensional mesh of a multiplicity of fine fibers which are connected together to create a great plurality of irregular liquid paths through the spaces between the fibers, the minimum thickness t_(min) (mm) of the element being determined by the equation:

    t.sub.min =(p×f)/.sub.20d

where p = pressure (psi) under which liquid is dispensed f = fibre fineness (decitex) d = density (kg/m³),said liquid being dispensed through said foam control element without introducing air to said liquid.
 7. A method of dispensing liquids according to claim 6, wherein the minimum thickness of the element is determined by the equation:

    t.sub.min =(p×f)/.sub.10d.


8. 8. A method of dispensing liquids according to claim 6, wherein the minimum thickness of the element is determined by the equation:

    t.sub.min =(p×f)/.sub.5d. 